In my pending U.S. patent application Ser. No. 492135 filed May 6, 1983, now U.S. Pat. No. 4,528,848.
I have disclosed an apparatus, as set forth above, of the type of a loop conveyer, comprising a housing including a side wall having an essentially cylindrical inner surface, an upper and a lower face wall provided with charging and discharging ports respectively and a rotor mounted in and sealed to the housing for rotation about a vertical axis. The rotor is provided with a plurality of laterally closed pockets and has a peripheral, cylindrical surface forming an annular interspace with the inner, cylindrical surface of the side wall of the housing. Pourable material, filled into the rotor through the charge port, is conveyed through a measuring path and then dischargedthrough the discharge port. With the known apparatus, the lower and upper face walls of the housing are in resilient engagement with the upper and lower faces of the rotor, which results in a noticeable friction between the engaging parts. Also, despite the sealings provided, some of the very fine particles of the pourable material, for instance coal dust, may penetrate out of the pockets into the interior of the rotor or into the interspace between the inner cylindrical surface of the housing and the peripheral cylindrical surface of the rotor.